Abstract Number: PB0345
Meeting: ISTH 2022 Congress
Background: Platelet glycoprotein VI (GPVI) receives interest when developing new antiplatelet drugs with low bleeding risk. GPVI interactions with collagen initiates thrombus formation and GPVI binding to fibrin(ogen) promotes thrombus growth and stability. To be considered to have the greatest efficacy, GPVI antagonists are expected to inhibit the interaction of GPVI with its main ligands. Glenzocimab is a clinical grade anti-GPVI humanized antibody fragment that inhibits GPVI interaction with collagen and fibrin(ogen).
Aims: To determine the mechanism of the glenzocimab’s inhibitory effect.
Methods: The extracellular domain of GPVI expressed as a monomer (GPVIex) or a dimer (GPVI-Fc) and GPVI-Fc des129-136, were produced and their interaction with glenzocimab analyzed by SPR and solid phase assays. A co-crystal of glenzocimab with GPVIex was obtained and the 1.9 Å structure compared to known GPVI structures (PBB ID: 2GI7 and 5OU7) and GPVI-CRP complex structures (PDB ID: 5OU8 and 5OU9).
Results: Glenzocimab binds to the D2 domain of GPVI. Rearrangements within this domain prevent D2 homotypic interactions and formation of GPVI dimers of high affinity for collagen and fibrin. Glenzocimab induces allosteric modifications within the D1 domain with alterations of the betaC and betaF strands in the CRP binding groove. A shift of the betaC strand results in movement of R38, a key residue into the CRP binding channel and to a direct clash with CRP. Moreover, the light variable region of the GPVI-bound Fab causes steric hindrance which prevents the CRP/collagen elongated chains to extend out of their binding site. Truncation of D2 residues 129-136 blocked binding to glenzocimab, validating the epitope localization.
Conclusion(s): This study demonstrates that altogether, the inhibition of GPVI-dimerization, allosteric modifications of the collagen-binding groove and steric hindrance by glenzocimab allow the inhibition of GPVI interactions with its major ligands.
To cite this abstract in AMA style:Billiald P, Slater A, Pugnière M, Jiacomini I, Welin M, Rose N, Toledano E, François D, Watson S, Jandrot-Perrus M. Targeting platelet Glycoprotein VI with Glenzocimab: a novel mechanism of inhibition [abstract]. https://abstracts.isth.org/abstract/targeting-platelet-glycoprotein-vi-with-glenzocimab-a-novel-mechanism-of-inhibition/. Accessed February 27, 2024.
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